Her advice is: urban planning to combat pollen

Author: Susanne Wenger

Marloes Eeftens – her Dutch first name is pronounced “Marlus” – can feel when it is spring by two things. Firstly, she herself has an allergic reaction to hazel, birch and grass pollen. Her nose runs, her eyes itch and she is more tired than usual. “I cancel outdoor appointments on days when the pollen count is particularly high”, she says. Secondly, representatives of the media contact her and ask questions, because Eeftens is a leading pollen researcher, as Swiss television called her. The 40-year-old environmental epidemiologist is leading a multi-year study at the Swiss Tropical and Public Health Institute (Swiss TPH) in Allschwil near Basel.

Eeftens and her team are investigating how pollen from trees, grasses and herbs affect the health of the population in Switzerland. The project, which was launched in 2020 and is co-funded by the EU, is called the Epochal study - an acronym for the English title “Effects of Pollen on Cardiorespiratory Health and Allergies”. The abbreviated name sounds like a programme: we live in an age in which allergies of all kinds are increasing massively. Pollen allergies are no exception. 100 years ago, less than 1% of the Swiss population was affected by them. Today, it is estimated that one in five people in Switzerland – almost 1.8 million people – have an allergic reaction to at least one type of pollen.

Increased blood pressure

“But there’s been hardly any research on pollens and they are not considered a public health issue”, says Eeftens. Unlike with particulate matter, noise or electromagnetic radiation, there are no limit values for pollen. “We don’t know from what concentration upwards pollen start to be harmful, nor do we know all the consequences,” she explains. One thing is clear: plants naturally release pollen. However, pollen – just like human-made environmental influences - can have many different health effects, says Eeftens. She believes the view which holds that allergy sufferers simply have to accept their chronic illness is wrong.

She and her team investigated the problem in greater depth – and found for the first time what researchers had previously only suspected: a pollen allergy goes beyond the well-known and annoying seasonal symptoms such as sneezing fits and irritated eyes. Pollen also affects the cardiovascular system. In a partial study published in 2024 with around 400 participants from the Basel region, allergy sufferers’ blood pressure increased when they were exposed to pollen. The pollen made no difference in participants with no allergies.

“I would like to see a rethink”

“Even low pollen concentrations had an effect on blood pressure, and the effect increased as the concentration rose,” states Eeftens. Women and overweight people were more severely affected, although the increase remained “rather small”. But because so many people have a pollen allergy, it can place a “heavy burden” on public health, according to the researcher. Furthermore, other studies showed that high pollen concentrations are associated with more hospital admissions.

One thing is certain: high blood pressure is a risk factor for cardiovascular diseases such as strokes. “I would like to see a rethink”, says Eeftens in the light of the new insights. She believes pollen allergies are not an individual problem, prevention should not be the sole responsibility of those affected. Public measures are needed, in her view. Urban planning affords opportunities: many Swiss cities want to plant significantly more trees to provide shade to cope with the increased number of heat waves. “It is important not to plant everywhere highly-allergenic trees that are used frequently, such as birch”, emphasizes Eeftens, as this also promotes biodiversity.

Academic work “is enjoyable”

Marloes Eeftens talks vividly and graphically about her research work. She came to the Swiss TPH 12 years ago as a postdoc from the Netherlands. Pollen were uncharted territory for her when she embarked on the Epochal study. Prior to that, she had been working on air quality and mobile phone radiation. In her dissertation at the University of Utrecht, she had investigated the impacts of air pollution on children’s lungs. “I like to immerse myself in new areas of research,” she says.  Eeftens grew up in a small village near Breda in the south of the Netherlands. “There was a lot of carnival, lots of strawberries,” she relates. She planted leeks in her first job: the smell was terrible,” she recalls with a laugh.

Eeftens lives with her husband and two daughters (aged 13 and 10) on the outskirts of Basel. She now speaks very good German – an advantage in the current naturalization process.  She likes Switzerland’s linguistic diversity, as well as the international environment at the Tropical and Public Health Institute with 1,000 employees from 96 nations. As an assistant professor at the University of Basel, she introduces students to environmental epidemiology.

“I enjoy academic work,” she says. The fact that a university career requires constant commitment and that one has to raise funding repeatedly is part of the job. If there’s anything typically Dutch about her, it’s pragmatism, she says. Her husband, who is a researcher himself and now self-employed, knows the requirements and supports her plans: “I really appreciate that.” Eeftens likes exchanging ideas with researchers from various disciplines at the Young Academy, of which she has been a member since 2020. “It’s rewarding.”

Educational work is necessary

Eeftens is currently evaluating further data from the Epochal study. In addition to blood pressure, the researchers also recorded heart rate variability, lung function, respiratory tract inflammations and cognitive performance. They also recorded general well-being. Eeftens relies on digital technology to obtain more data. Together with the “aha! Swiss Allergy Centre”, she is developing an app in which allergy sufferers can enter their symptoms. “This enables us to better understand links with pollen concentrations,” she points out. She has also developed a model that depicts the spatial and temporal distribution of the pollen count. It uses the MeteoSwiss measurement network. “This enables us to know retrospectively the degree to which people were exposed on a particular day.”

Pollen will therefore continue to keep Marloes Eeftens busy for some time to come – and for good reason. Due to global warming, the pollen season in Switzerland starts earlier and is more intensive than it was 30 years ago. “This exacerbates the suffering of people with pollen allergies,” she points out. A lot of educational work remains to be done. Eeftens points through the window to a construction site near her workplace in the modern “BaseLink” area where many life science companies are located. 20 birch trees have been planted near a building under construction. “Birch pollens are one of the strongest allergens – along with alder, ash, hazel, grasses, mugwort and ragweed,” she warns and adds:  “With a better knowledge of allergenic plant species and smart environmental design, we could do a lot more for prevention.”